This invention relates to a copper-based alloy connector which is so excellent in electrical conductivity, adherence of solder of the connector when bent, high-temperature creep strength, and migration resistance as to withstand use in a high-temperature and high-humidity environment.
Conventionally, a copper-based alloy having a chemical composition consisting essentially by weight percent of 1.5 to 9% tin (Sn), 0.03 to 0.35% phosphorus (P), and the balance of copper (Cu) and inevitable impurities (hereinafter referred to as "phosphor bronze") has generally been used as a material for connectors for use in various electrical devices.
However, in recent years, it has been required for connectors of this kind to be smaller in size, particularly in thickness, with more complicated shapes, but to have increased electrical conductivity, in order to meet increasing demand for reduced size, increased output capacity, and increased wiring density of electrical devices.
Further, as the output capacity and hence the wiring density increase with decrease in the sizes of electrical devices, connectors often have to be arranged at short intervals, so that heat developed in the connectors is not easily dissipated, resulting in overheating of the connectors. Therefore, high-temperature strength has been required of connectors.
Furtheremore, recently, electrical devices with increased wiring density in which connectors are arranged at short intervals have been used in automotive vehicles, small-sized ships, etc. which are frequently operated in high temperature and high humidity environments where they can sometimes be splashed with water. In such high-temperature and high-humidity environments, moisture or water attached on the connectors can react with metallic elements forming the connectors to cause ionization of the metallic elements. Positive ions move to the cathode of the connector (migration), whereby metallic crystal grains grow in the structure of the connector, which sometimes results in short circuit between the connectors arranged at short intervals. The conventional connectors, which are reduced in size and complicated in shape, have short distances between the electrodes. Therefore, they cannot fully exhibit their proper functions. Further, when the connectors are used in an automotive vehicle or a small-sized ship, they are subject to vibrations and bending forces applied thereto, causing exfoliation of solder.